Are you near the Hayden Planetarium this evening? Look up! You’ll see Hubble spectra inscribed in laser light across the face of the Hayden sphere. These strange lines are the telescope’s observations of light from distant, cosmic objects. While these spectra are quite complicated, you can identify some of the objects by looking for the basic shapes described in our field guide below.
A galaxy’s spectrum is the combined light of its many billions of stars. For starburst galaxies, in which stars are forming abundantly, the spectrum shows strong peaks due to the hot gas in star-forming clouds.
HOT BLUE STARS
This spectrum peaks near the blue end of the scale, indicating that it is produced by a blue star. Blue stars are young, massive stars, glowing extremely hot. Their temperatures start at about 15,000 degrees Kelvin and can rise as high as 30,000 K. Blue stars burn through their fuel quickly and have short life spans.
This spectrum also peaks near the blue end of the scale. This shape reveals the dominant presence of many blue stars, indicating that this object is probably either a group of blue stars or a spiral galaxy. Because spiral galaxies tend to have active star formation, they often contain large populations of young, blue stars.
COOL RED STARS
To astronomers, a "cool" star has a surface temperature of about 3,000 degrees Kelvin and shines mostly in red and infrared light. Molecules in the star’s atmosphere absorb light and produce the dips visible in this spectrum.
This spectrum peaks at the red end of the scale, indicating the presence of a large number of old, red stars. This information reveals that this object is a likely an elliptical galaxy. Elliptical galaxies are the universe’s oldest galaxies, and contain aged stars that are roughly 10 billion years old.