The Study of Climate on Alien Worlds
“Characterizing atmospheres beyond the Solar System is an endeavor no longer confined to the realm of science fiction.”
NGC 4261’s off-kilter globular cluster population
We think many galaxies we see today had mergers and interactions in their past, but how can we know for sure? Bonfini et al. look to evidence from a subtle pattern in the distribution of globular clusters in NGC 4261.
An asteroid rotation factory
Title: Asteroid rotation periods from the Palomar Transient Factory survey Authors: D. Polishook, E. O. Ofek, A. Waszczak, S. R. Kulkarni, A. Gal-Yam, O. Aharonson, R. Laher, J. Surace, C. Klein, J. Bloom, N. Brosch, D. Prialnik, C. Grillmair et al. First Author’s Institution: Benoziyo Center for Astrophysics, Weizmann Institute of Science, IsraelDetermination of the rotation periods of asteroids has a number of applications. When considering an asteroid individually, it can help one to understand the physical properties of an individual asteroid, including its shape and whether or not it’s a binary. In a statistical sense, the rotations of the entire population of asteroids can help one to understand the physical processes that govern asteroid rotation. The two mechanisms that influence an asteroid’s rotatation are collisions and something called the YORP effect, in which photons from the Sun are actually able to accelerate asteroids through absorption and re-emission. There’s a nice discussion of this type of science which includes a description of the YORP effect in this Cornell press release, while this Discovery news story reports on the first direct detection of the YORP effect (which combines the initials of four different people).*Currently there are 3,700 asteroids with measured rotation periods; using the Palomar Transient Factory, these authors aim to eventually measure rotation periods for 10,000 asteroids. (PTF also finds supernovae, see for example this discovery). In this paper, Polishook et al. report on the identification of 624 asteroids in the PTF survey, 20% of which are new discoveries, and 88 new rotation period measurements. All of the asteroids identified belong to the main asteroid belt. The smallest asteroids...How do astronomers measure the brightness of something?
Sounds like a simple question. When you go out and look at the stars at night with your naked eye, you might be able to pretty easily sort out which stars are the brightest, which are the faintest, and come up with some ranking of them for those in between. Now, do this with telescopes…
Looking back in time with DASCH
How do stars vary on a hundred year time scale? The DASCH (Digital Access to a Sky Century @ Harvard) Team has been looking back at data taken over the last century in order to answer this question. This paper reports the most recent DASCH discovery, which concerns the star KU Cyg. This is an eclipsing binary system in which a more massive F star is gaining mass from a red giant. The authors noticed a 0.5 magnitude drop in the brightness of the star around 1900 that lasts for five years.
Studying stellar activity with CoRoT
Stellar variability has received more attention recently due to the problems it poses in the detection of exoplanets; however the study of variability is a field of its own. What causes activity? How does magnetic activity vary with different stars? This paper looks at results from the CoRoT satellite (for Convection, Rotation and planetary Transits), which was launched in December of 2006. This paper is concerned with the long-term photometric microvariability of stars and how stellar activity relates to rotation period and temperature.