At the center of the Milky Way galaxy, nearly 26,000 light-years away, a cluster of stars circles close to the supermassive black hole known as Sagittarius A*. As these few dozen stars, called S-stars, approach the black hole—which is about four million times more massive than the sun—its immense gravitational force whips them around faster than 16 million miles per hour. In fact, the gravitational pull of Sagittarius A* is so intense that it warps the light from these stars when they stray too close, stretching the wavelengths toward the red part of the electromagnetic spectrum. Continue reading A Star Orbiting in the Extreme Gravity of a Black Hole Validates General Relativity
At the center of a galaxy called Messier 87, about 55 million light-years away, about which all of the matter of the galaxy orbits, there lies a monster: a supermassive black hole. With about 6.5 billion times the mass of the sun, the black hole at the center of M87 is so dense that its escape velocity, or the velocity needed to escape the object’s gravity, is more than the speed of light. Accordingly, not even photons of light can escape once they wander too close.
The early universe was filled with strange and mysterious objects. Shortly after the Big Bang, large clouds of material may have formed black holes directly, without first coalescing into stars as we see today. Pseudo-galaxies lit up a sea of neutral hydrogen to make the universe transparent, releasing photons where before there was nothing but darkness. And short-lived stars made of nothing but hydrogen and helium may have flashed in and out of existence like sparks in the night. Continue reading Four Types of Stars That Will Not Exist for Billions or Even Trillions of Years
The most distant planetary exploration in history required a significant amount of careful planning and preparation, as well as a little bit of luck.
Mars may have a hostile, dusty exterior bathed in dangerous radiation, but a new study suggests that it’s possible life could exist under that inhospitable crust. Pockets of salty water with enough dissolved oxygen to support life may be present in certain parts of the planet, according to a new paper published in the journal Nature Geoscience. Continue reading Salty Water Under the Surface of Mars Could Have Enough Oxygen for Life
The Cassini space probe’s fatal plummet into Saturn has revealed that the gas giant’s innermost ring sheds icy showers of rain and organic molecules into the planet’s upper atmosphere at an incredible rate.
Traveling to Mars is the next great step in humanity’s space journey. In Hollywood, the recent movie The Martian and television series The First present reaching the Red Planet as more of a near-term logistics challenge rather than a pie-in-the-sky space dream. NASA is currently orienting itself toward a “Moon to Mars” Mission, but the technical hurdles facing a Mars mission are still massive. One of the most difficult challenges is dealing with the dose of radiation any interplanetary astronauts would face. Meghan Bartels at Space.com reports that new data from the European Space Agency (ESA) has refined our model for radiation during the journey to and from Mars, and it doesn’t look good. Continue reading Explorers Will Face Dangerous Amounts of Radiation On Their Trip to Mars