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Science and reason is all about... science and reason. News and explanations of recent developments in the most intriguing branches of science. Philosophical and political issues of relevance are also discussed.
Charles Daney
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- February 27, 2011
- 10:26 PM
- 329 views
Telomerase can reverse the aging process... sort of
by Charles Daney in Science and Reason
Biologists are, at long last, beginning to understand the molecular processes responsible for aging in complex (multicellular) organisms – and to investigate ways to counteract these processes. We discussed one line of research in this recent article about a particular sirtuin (SIRT3) that helps relieve oxidative stress that can lead to DNA damage, which generally leads, in turn, to cell senescence or death.While oxidative stress is certainly a significant factor in aging, possibly the mos........ Read more »
Jaskelioff, M., Muller, F., Paik, J., Thomas, E., Jiang, S., Adams, A., Sahin, E., Kost-Alimova, M., Protopopov, A., Cadiñanos, J.... (2010) Telomerase reactivation reverses tissue degeneration in aged telomerase-deficient mice. Nature, 469(7328), 102-106. DOI: 10.1038/nature09603
- February 20, 2011
- 11:40 PM
- 566 views
Supermassive black hole in a dwarf galaxy
by Charles Daney in Science and Reason
Supermassive black hole in a type of galaxy where nobody expected to find one? Henize 2-10 is a small, mostly unremarkable compact dwarf galaxy. Its estimated dynamical mass is about 1010 M⊙, only a few percent of our galaxy's mass, and its distance from us is about 30 million light years. It is irregular in shape and does not fit in any category of the standard Hubble sequence.The only respect in which Henize 2-10 has attracted attention – for several decades – before now is a........ Read more »
Reines, A., Sivakoff, G., Johnson, K., & Brogan, C. (2011) An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10. Nature, 470(7332), 66-68. DOI: 10.1038/nature09724
- February 7, 2011
- 03:56 AM
- 307 views
Testing the Fountain of Youth in the lab
by Charles Daney in Science and Reason
It's been more than 10 years since it was noticed that certain enzymes – the sirtuins – had life-extending properties in organisms like yeast, and later nematodes, fruit flies, and mice. The excitement spread to other compounds, such as resveratrol, that seemed to activate or assist sirtuins. Hopes were high that such things might offer the known longevity benefits of calorie restriction in a pill form. Ever since then the gold rush has been on to figure out how these things work &nd........ Read more »
Someya, S., Yu, W., Hallows, W., Xu, J., Vann, J., Leeuwenburgh, C., Tanokura, M., Denu, J., & Prolla, T. (2010) Sirt3 Mediates Reduction of Oxidative Damage and Prevention of Age-Related Hearing Loss under Caloric Restriction. Cell, 143(5), 802-812. DOI: 10.1016/j.cell.2010.10.002
- January 16, 2011
- 11:11 PM
- 398 views
What activates a supermassive black hole?
by Charles Daney in Science and Reason
There's good evidence that massive black holes exist at the centers of most large galaxies having a central bulge, and even within galaxies that lack a central bulge, are small, or have an irregular form. Such black holes can range in size up to more than 10 billion solar masses (M⊙). Little is known about what the average or typical mass of a central black hole is, although most are probably a lot smaller, such as that of Sagittarius A* in our galaxy, which is only ~4.2×106 M⊙........ Read more »
Cisternas, M., Jahnke, K., Inskip, K., Kartaltepe, J., Koekemoer, A., Lisker, T., Robaina, A., Scodeggio, M., Sheth, K., Trump, J.... (2011) THE BULK OF THE BLACK HOLE GROWTH SINCE ∼ 1 OCCURS IN A SECULAR UNIVERSE: NO MAJOR MERGER-AGN CONNECTION . The Astrophysical Journal, 726(2), 57. DOI: 10.1088/0004-637X/726/2/57
- August 8, 2010
- 10:39 PM
- 470 views
What does marathon running do to an athlete's cells?
by Charles Daney in Science and Reason
If you've ever taken up running as a form of exercise, or even thought about it, there's a certain paradox that may have occurred to you. The health benefits of aerobic exercise are well-documented. (See here, for example.) In particular such exercise has been shown to reduce risks of cardiovascular disease, diabetes, and some forms of cancer. Beneficial physiological effects include reduction of high blood pressure, better control of blood sugar, and reducing blood levels of low-density lipopro........ Read more »
Marfe, G., Tafani, M., Pucci, B., Di Stefano, C., Indelicato, M., Andreoli, A., Russo, M., Sinibaldi-Salimei, P., & Manzi, V. (2010) The effect of marathon on mRNA expression of anti-apoptotic and pro-apoptotic proteins and sirtuins family in male recreational long-distance runners. BMC Physiology, 10(1), 7. DOI: 10.1186/1472-6793-10-7
- July 17, 2010
- 11:35 PM
- 519 views
Quasars in the very early universe
by Charles Daney in Science and Reason
Quasars are powered by the gravitational (potential) energy of their central supermassive black holes. However, their distinctive features – their extremely high luminosity in particular – are very dependent on characteristics of matter close to the black hole. Most supermassive black holes (SMBH), including those at the centers of the Milky Way and our close neighbor M31 (Andromeda), are responsible for fairly small amounts of radiation in any part of the electromagnetic spectrum. T........ Read more »
Jiang, L., Fan, X., Brandt, W., Carilli, C., Egami, E., Hines, D., Kurk, J., Richards, G., Shen, Y., Strauss, M.... (2010) Dust-free quasars in the early Universe. Nature, 464(7287), 380-383. DOI: 10.1038/nature08877
- June 28, 2010
- 12:27 AM
- 655 views
Creativity and mental illness
by Charles Daney in Science and Reason
The association between creativity and mental illness is sort of a cliché – but that doesn't mean there's nothing to it. Standard examples given include Vincent van Gogh, Robert Lowell, and John Nash.There has been a rather large amount of research into the connection, and a large number of biographical accounts of famous creative people who also suffered from mental illness. But the neurobiological details are emerging only slowly. After all, our understanding of the biological roo........ Read more »
de Manzano, �., Cervenka, S., Karabanov, A., Farde, L., & Ullén, F. (2010) Thinking Outside a Less Intact Box: Thalamic Dopamine D2 Receptor Densities Are Negatively Related to Psychometric Creativity in Healthy Individuals. PLoS ONE, 5(5). DOI: 10.1371/journal.pone.0010670
- May 12, 2010
- 11:24 PM
- 504 views
Where the action is in black hole jets
by Charles Daney in Science and Reason
The object known simply as 3C 279 is rather distinctive for several reasons, in spite of the rather unassuming name. For one thing it's an active galaxy – that is, it has a supermassive black hole at its center, and that black hole is sucking in surrounding matter at a rate high enough to generate as much energy as all stars the in the galaxy where it resides combined. Only about 1% of visible galaxies are active galaxies like 3C 279.But that's not all. 3C 279 is also a radio galaxy, a sub........ Read more »
Abdo, A., Ackermann, M., Ajello, M., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B., Bechtol, K.... (2010) A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279. Nature, 463(7283), 919-923. DOI: 10.1038/nature08841
- April 25, 2010
- 11:42 PM
- 587 views
Active galaxies and supermassive black hole jets
by Charles Daney in Science and Reason
Most galaxies have a supermassive black hole in their center – sometimes even more than one. These black holes can have masses up to ten billion solar masses (1010 M⊙) or more. One of the largest known examples is part of a binary system, and it weighs in at 1.8×1010 M⊙ – see here, here, or here. (There are exceptions, such as the nearby M33, which apparently does not have a central black hole of mass more than 3000 M⊙.)All black holes gravitationally attract ........ Read more »
Evans, D., Reeves, J., Hardcastle, M., Kraft, R., Lee, J., & Virani, S. (2010) THE HARD X-RAY VIEW OF REFLECTION, ABSORPTION, AND THE DISK-JET CONNECTION IN THE RADIO-LOUD AGN 3C 33. The Astrophysical Journal, 710(1), 859-868. DOI: 10.1088/0004-637X/710/1/859
- March 12, 2010
- 03:01 AM
- 591 views
Galaxies are slowly running out of gas
by Charles Daney in Science and Reason
Galaxies are made of stars, and stars are made of... gas. So a large part of understanding how galaxies evolve and grow is understanding how much "gas" (literally, not "gasoline") is present in galaxies – but has not yet been incorporated in stars – at different periods in the history of the universe.What periods of the universe are most interesting in this regard? The answer is: periods somewhat less than the first half of the universe's existence since the time of the big bang, rou........ Read more »
Tacconi, L., Genzel, R., Neri, R., Cox, P., Cooper, M., Shapiro, K., Bolatto, A., Bouché, N., Bournaud, F., Burkert, A.... (2010) High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature, 463(7282), 781-784. DOI: 10.1038/nature08773
- March 7, 2010
- 05:04 AM
- 575 views
Gamma-ray bursts without the gamma rays?
by Charles Daney in Science and Reason
We discussed supernovae a bit in this recent post on gamma-ray bursts. There is now interesting new information on the connection between supernovae and gamma-ray bursts from two recently-described supernovae with atypical properties.Let's first review a little. Gamma-ray bursts (GRBs) are identified by detection of relatively brief (usually less than a few minutes) but highly energetic emissions of gamma rays. Although there's a great deal of diversity, most events fall into one of two categori........ Read more »
Soderberg, A., Chakraborti, S., Pignata, G., Chevalier, R., Chandra, P., Ray, A., Wieringa, M., Copete, A., Chaplin, V., Connaughton, V.... (2010) A relativistic type Ibc supernova without a detected γ-ray burst. Nature, 463(7280), 513-515. DOI: 10.1038/nature08714
Paragi, Z., Taylor, G., Kouveliotou, C., Granot, J., Ramirez-Ruiz, E., Bietenholz, M., van der Horst, A., Pidopryhora, Y., van Langevelde, H., Garrett, M.... (2010) A mildly relativistic radio jet from the otherwise normal type Ic supernova 2007gr. Nature, 463(7280), 516-518. DOI: 10.1038/nature08713
- February 27, 2010
- 10:06 PM
- 544 views
Spiral galaxies are taking over
by Charles Daney in Science and Reason
Everybody knows what a spiral galaxy looks like. Here's a typical nearby example (M74):Among the largest and brightest galaxies close to our own, about 72% are of this spiral type, like M74. There is a classification system for galaxy shapes, and the remaining 28% of large, bright, nearby galaxies fall into classes called "elliptical", "lenticular", or simply "peculiar". (For simplicity and for other reasons that will become apparent, we're ignoring smalle........ Read more »
Delgado-Serrano, R., Hammer, F., Yang, Y., Puech, M., Flores, H., & Rodrigues, M. (2010) How was the Hubble sequence 6 Gyr ago?. Astronomy and Astrophysics. DOI: 10.1051/0004-6361/200912704
- February 24, 2010
- 03:06 AM
- 585 views
Where have all the protons gone?
by Charles Daney in Science and Reason
Astronomers have long known that there is a rather close relationship between the intrinsic luminosity of a spiral galaxy and the rotational velocity of stars (around the galactic center) in the outer portions of the galaxy. This relationship even has a name: the Tully-Fisher relation.It has also been known that small, nearby dwarf galaxies, which are irregular in shape, are not nearly as bright as they "should" be, according to the Tully-Fisher relation, given the measured average velocities of........ Read more »
McGaugh, S., Schombert, J., de Blok, W., & Zagursky, M. (2010) THE BARYON CONTENT OF COSMIC STRUCTURES. The Astrophysical Journal, 708(1). DOI: 10.1088/2041-8205/708/1/L14
- February 22, 2010
- 02:15 AM
- 613 views
Dwarf galaxies start making sense
by Charles Daney in Science and Reason
Cosmology has, for a decade, had its "standard model", which largely explains most of the cosmological phenomena that astronomers are able to observe. Except for a relatively small number of things that don't seem to make sense in the model. Prominent among the latter are dwarf galaxies – by one definition, galaxies having less than 10% of the total mass of the Milky Way.The standard model of cosmology is known officially as the Λ-cold-dark-matter model – ΛCDM. (This th........ Read more »
Governato, F., Brook, C., Mayer, L., Brooks, A., Rhee, G., Wadsley, J., Jonsson, P., Willman, B., Stinson, G., Quinn, T.... (2010) Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows. Nature, 463(7278), 203-206. DOI: 10.1038/nature08640
- February 15, 2010
- 10:46 PM
- 471 views
Far out!
by Charles Daney in Science and Reason
If you're interested in something out of the ordinary, astronomically speaking, the best place to look for the exotic may be as far away (in both space and time) as possible.Perhaps that's why I like to consider really far out stuff, like the most distant gamma-ray burst seen yet. Or maybe I just like to get away from the depressing chaos and confusion of "modern" life.In any case, there's always something new, just beyond the farthest thing we've seen yet. That far-out gamma-ray burst (GRB 0904........ Read more »
R. J. Bouwens, G. D. Illingworth, I. Labbe, P. A. Oesch, M. Carollo, M. Trenti, P. G. van Dokkum, M. Franx, M. Stiavelli, V. Gonzalez.... (2009) Constraints on the First Galaxies: z~10 Galaxy Candidates from HST WFC3/IR. Nature. arXiv: 0912.4263v2
- January 31, 2010
- 12:31 AM
- 652 views
Magnetic fields in gamma-ray burst jets
by Charles Daney in Science and Reason
Gamma-ray bursts (GRBs) are the most dramatic short-lived violent events observed in the universe. They are often described as releasing a quantity of energy, in less than a minute, that is at least as much as a star like the Sun releases in its entire 10 billion year lifetime. Since the first detection of a gamma-ray burst in 1967, the central question has been to determine the nature of the process or processes that can release so much energy so quickly.We've discussed gamma-ray burst several ........ Read more »
Steele, I., Mundell, C., Smith, R., Kobayashi, S., & Guidorzi, C. (2009) Ten per cent polarized optical emission from GRB 090102. Nature, 462(7274), 767-769. DOI: 10.1038/nature08590
- January 4, 2010
- 03:07 AM
- 606 views
Space is very fine-grained
by Charles Daney in Science and Reason
It would take you a lot longer to hike a significant distance over very hilly terrain than it would over a completely flat plain. For much the same reason, it would take light longer to cover the same distance depending whether the space through which it moves does or doesn't have large "hills".But what does it mean for space to contain "hills"? And how large do "hills" need to be to make a difference?Consider the second question first. There's no natural place on Earth that is perfectly flat, o........ Read more »
Abdo, A., Ackermann, M., Ajello, M., Asano, K., Atwood, W., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Baring, M.... (2009) A limit on the variation of the speed of light arising from quantum gravity effects. Nature, 462(7271), 331-334. DOI: 10.1038/nature08574
- November 2, 2009
- 01:26 AM
- 661 views
Most Distant Known Object In The Universe
by Charles Daney in Science and Reason
On April 23 of this year the Swift Gamma-Ray Burst Telescope detected, just as it was designed to do, a gamma-ray burst (GRB). Within less than a day two of the most powerful Earth-based telescopes had begun studying the quickly fading light of the object, known as GRB 090423. (There were other observatories investigating it as well.)Because the light from GRBs fades so rapidly, most such objects are detected from space-based instruments that are especially designed for the purpose, like Swift. ........ Read more »
Tanvir, N., Fox, D., Levan, A., Berger, E., Wiersema, K., Fynbo, J., Cucchiara, A., Krühler, T., Gehrels, N., Bloom, J.... (2009) A γ-ray burst at a redshift of z ≈ 8.2. Nature, 461(7268), 1254-1257. DOI: 10.1038/nature08459
Salvaterra, R., Valle, M., Campana, S., Chincarini, G., Covino, S., D’Avanzo, P., Fernández-Soto, A., Guidorzi, C., Mannucci, F., Margutti, R.... (2009) GRB 090423 at a redshift of z ≈ 8.1. Nature, 461(7268), 1258-1260. DOI: 10.1038/nature08445
- October 26, 2009
- 02:22 AM
- 658 views
A surprisingly compact early galaxy
by Charles Daney in Science and Reason
Astronomers are beginning to learn significant details of the structure of galaxies in the early universe. And what they're learning is rather surprising: at least some early galaxies are almost as massive as otherwise similar galaxies in the present universe, yet they are much smaller in linear size, by a factor of five, thus much more compact.What time period are we talking about here? It's not actually the time that the earliest galaxies formed, which was less than a billion years after the b........ Read more »
van Dokkum, P., Kriek, M., & Franx, M. (2009) A high stellar velocity dispersion for a compact massive galaxy at redshift z . Nature, 460(7256), 717-719. DOI: 10.1038/nature08220
- October 10, 2009
- 05:15 AM
- 721 views
Telomerase and Wnt signaling
by Charles Daney in Science and Reason
Now that research into telomeres and telomerase has (finally) garnered a Nobel Prize, it's a good time to write about recent research on the subject.Seminal work on telomeres by Elizabeth Blackburn, one of the Nobel winners, was published way back in 1978, and active studies have been going on ever since. So perhaps it's not surprising that the rate of new findings is not so rapid as occurs in newer areas – such as stem cells.But fascinating new results on telomeres and telomerase do still........ Read more »
Park, J., Venteicher, A., Hong, J., Choi, J., Jun, S., Shkreli, M., Chang, W., Meng, Z., Cheung, P., Ji, H.... (2009) Telomerase modulates Wnt signalling by association with target gene chromatin. Nature, 460(7251), 66-72. DOI: 10.1038/nature08137
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