What’s in a Name?

This galaxy is called 2XMM J143450.5+033843. That may seem like some random collection characters, but the name is meaningful to an astronomer. The first four characters show that it was discovered during the second sky survey performed by ESA’s XMM-Newton satellite—2XMM.  The characters following the J are its address in the sky: a right ascension of 14h (hours) 34m (minutes) 50.5s (seconds) and a declination of +03d (degrees) 38m (minutes) 43s (seconds).

2XMM J143450.5+033843 is almost 400 million light-years from Earth. It is a Seyfert galaxy that is dominated by a supermassive black hole that is pumping out vast amounts of radiation from its galactic core.

Image Credit: ESA / NASA

Speeding Stars

This video was constructed using data derived from observations by ESA’s Gaia satellite. It starts with the stars shown in their positions as of a bit more than a million years ago, tracks the changes in their positions up to the present day, and ends with a view of the sky as seen by Gaia between 2014 and 2015. The trajectories highlighted in yellow show six unusual stars that are moving through the Milky Way at hypervelocities of several hundred km/s. Most likely, these stars’ high speeds are the results of past interactions with the supermassive black hole that sits at the center of the galaxy. Analysis of their paths provides information about the gravitational field of the Milky Way from the center to its outskirts.

One of the six stars (numbered 1) is moving at over 500 km/s, which is above escape velocity for the galaxy. It will eventual fly off into intergalactic space. The other five stars are somewhat slower and are still bound to the galaxy.

Video Credit: ESA

A Pair of Lonely Dwarfs

Luhman 16AB is a double star system composed of two brown dwarfs. It’s only about six light-years away, and is the third closest stellar system to Earth—after the triple star system Alpha Centauri and Barnard’s Star. Because the brown dwarfs are so dim, Luhman 16AB was only discovered in 2013.

This series of dots with varying spacings between them in the image above shows the slow waltz of the two brown dwarfs. It’s a composite of 12 images made over the course of three years by the Hubble Space Telescope. Using high-precision astrometry, a team of astronomers tracked the two components of the system as they moved both across the sky and around each other.

The brown dwarfs, Luhman 16A and Luhman 16B, orbit each other at a distance of only about 500,000,000 km, roughly three times the distance between the Earth and the Sun. Observations of the system require high resolution. The astronomers using Hubble to study Luhman 16AB were not only interested in the waltz of the two starss as they orbited each other but also were also searching for a third, invisible partner. Earlier ground-based observation suggested the presence of an exoplanet in the system, but the Hubble data showed that the two dwarfs are indeed dancing alone, unperturbed by a massive planetary companion.

Image Credit: NASA / ESA