Big Bang Theory & Hubble's Law Explorer

Mission Accomplished!

You have successfully recreated Hubble's historic discovery and proved the universe is expanding.

Assessment Score

Status

Submitted ✓

Cosmic Standard Candles

Galaxies are vast oceans of hundreds of billions of stars. From Earth, their light usually blends into a fuzzy, inseparable glow. But occasionally, a few special stars stand out: Cepheid Variables.

Pre-Flight Knowledge Check

1. How are Cepheids different from other stars of a galaxy?

They are made entirely of dark matter. They physically expand and contract, pulsing in brightness. They do not move through space.

2. What did Henrietta Swan Leavitt determine about the period of the stars?

Shorter period = greater intrinsic brightness. The longer the period, the greater the intrinsic brightness. The period depends strictly on the galaxy's size.

3. What good does it do for astronomers to know the intrinsic brightness of a star?

It tells us the star's exact age in millions of years. It reveals if the star has habitable exoplanets. We can compare it to its apparent brightness to calculate exact distance.

Telescope Targeting

Targeting System

Status: No star targeted. Click a pulsing star.

Target star to gather data

Photometry (Period)

Drag the calipers (T1 & T2) to two consecutive peaks to measure the period.

Measured Period

0.0d

0 days 30 days 60 days

Target star and Gather Data to view spectra

Spectrometer (Velocity)

Compare the observed wavelength (λ_obs) of the galaxy to the Reference Lab Spectrum (λ₀) below.

Reference Lab (λ₀) 400.00 nm

Observed Galaxy (λ_obs) 380.00 nm

380 nm 580 nm 780 nm

Analysis Lab

Gather Data First

1 Calculate Distance (D)

Measured Period (days)

Luminosity (L = Period × 1000)

Sensor Brightness (B)

Calculated Distance (Mpc)

Gather Data First

2 Calculate Velocity (v)

Measured Wavelength (nm)

Redshift (z = (λ - 400) / 400)

Velocity (km/s)

Scientific Calculator

Observation Log

Galaxy	Period (d)	Dist (Mpc)	λ obs (nm)	Redshift z	Vel (km/s)
No observations recorded yet. Select a galaxy above to begin.

Hubble's Law

Mission Accomplished!

Cosmic Standard Candles

Leavitt's Law

The Cosmic Yardstick

Pre-Flight Knowledge Check

Hubble's Law & The Expanding Universe

Telescope Targeting

Targeting System

Photometry (Period)

Spectrometer (Velocity)

Analysis Lab

1 Calculate Distance (D)

2 Calculate Velocity (v)

Scientific Calculator

Observation Log

Hubble's Law Plot

Conclusions

Final Assessment

Assessment Complete!