Hubble’s Variable Nebula


What causes Hubble’s Variable Nebula to vary? The unusual nebula featured here changes its appearance noticeably in just a few weeks. Discovered over 200 years ago and subsequently cataloged as NGC 2261, the remarkable nebula is named for Edwin Hubble, who studied it early last century.

Hubble's Variable Nebula

This featured image was taken by another namesake of Hubble: the Space Telescope. Hubble’s Variable Nebula is a reflection nebula made of gas and fine dust fanning out from the star R Monocerotis.

The faint nebula is about one light-year across and lies about 2500 light-years away towards the constellation of the Unicorn (Monocerotis).

The leading variability explanation for Hubble’s Variable Nebula holds that dense knots of opaque dust pass close to R Mon and cast moving shadows onto the reflecting dust seen in the rest of the nebula.

Image Credit: Hubble, NASA, ESA; Data: Mark Clampin (NASA’s GSFC); Processing & License: Judy Schmidt

What Is Dark Matter?


For the first 150 million years after the Big Bang, there were no galaxies or stars or planets. The universe was featureless.

As time passed, the first stars formed. Stars collected into galaxies. Galaxies began to cluster together. Those clusters are made up of the galaxies and all the material between the galaxies. Clumps of matter in smashed into each other, and the planets in our solar system began to form around the sun.

Something must hold our solar system, galaxies and clusters of galaxies together. And gravity is that “glue.”

Continue reading “What Is Dark Matter?”

Dark Matter in a Simulated Universe


Is our universe haunted? It might look that way on this dark matter map. The gravity of unseen dark matter is the leading explanation for why galaxies rotate so fast, why galaxies orbit clusters so fast, why gravitational lenses so strongly deflect light, and why visible matter is distributed as it is both in the local universe and on the cosmic microwave background.

Dark Matter in a Simulated Universe

The featured image above is from the American Museum of Natural History’s Hayden Planetarium Space Show Dark Universe highlights one example of how pervasive dark matter might haunt our universe. In this frame from a detailed computer simulation, complex filaments of dark matter, shown in black, are strewn about the universe like spider webs, while the relatively rare clumps of familiar baryonic matter are colored orange.

These simulations are good statistical matches to astronomical observations. In what is perhaps a scarier turn of events, dark matter — although quite strange and in an unknown form — is no longer thought to be the strangest source of gravity in the universe. That honor now falls to dark energy, a more uniform source of repulsive gravity that seems to now dominate the expansion of the entire universe.


Illustration Credit & Copyright Tom Abel & Ralf Kaehler (KIPAC, SLAC), AMNH

Aurora over Iceland


This image was taken on a dark and stormy night in 2013 at Hverir, a geothermally active area along the volcanic landscape in northeastern Iceland. Geomagnetic storms produced the auroral display in the starry night sky while towers of steam and gas venting from fumaroles danced against the eerie greenish light.

Aurora over Iceland

Hverir is an area with hot springs in the north of Iceland . Hverir means in Icelandic whatsoever hot springs . It is located just east of Lake Mývatn about 6 kilometers south of the Krafla area near the Námaskarð mountain pass. T

he pastel area is one of Iceland ‘s largest solfather fields . It is lined with steam plumes, solariums, fumaroles and boiling mud pots of various sizes. A climb to the sulfurpowdered peak of the Námafjall mountain (432 meters) provides a panoramic view. Each is located directly next to Iceland ‘s ring road and is therefore easily accessible.

Image Credit & Copyright: Stéphane Vetter (Nuits sacrées)